Method and apparatus for reproducing data and method and apparatus for recording and/or reproducing data

ABSTRACT

A method and apparatus for recording or reproducing data in which high performance encoding and a high efficiency decoding are realized to lower the decoding error rate. A magnetic recording and/or reproducing apparatus  50  includes, in a recording system, a modulation encoder  52  for modulation encoding input data in a predetermined fashion and an interleaver  53  for interleaving data supplied from the modulation encoder  52  to re-array the data sequence. The magnetic recording and/or reproducing apparatus  50  also includes, in a reproducing system, a first deinterleaver for interleaving the input data for re-arraying the data sequence so that the bit sequence of data re-arrayed by the interleaver  53  will be restored to its original bit sequence, a modulation SISO decoder for modulation decoding data supplied from the first deinterleaver and a second deinterleaver for interleaving data corresponding to a difference value between data output by the modulation SISO decoder and data output by the first deinterleaver to re-array the data sequence of the difference data.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and apparatus for recording data on arecording medium, a method and apparatus for reproducing data recordedon a recording medium and a method and apparatus for recording and/orreproducing data for a recording medium.

2. Description of Related Art

As a recording medium for recording digital data, there are known a widevariety of recording mediums of the magnetic, optical or photomagneticsystem, such as a hard disc, a so-called DVCR (digital video cassetterecorder) or a so-called CD (Compact Disc), DVD (digital versatile disc)and a so-called MO (magneto-optical disc).

For recording signals on these recording mediums, physical processingneeds to be performed on the recording mediums, such as by controllingthe direction of magnetization by a write head for a recording medium ofthe magnetic recording system, or by forming pits of lengthscorresponding to signals by a stamper for a recording medium of theoptical recording system. In this case, in order to permit amplitudecontrol of readout signals or clock reproduction on the reproducing sidereading out the signals recorded on the recording medium to operate asnormally, the signal recording side for recording signals on a recordingmedium routinely uses a system of modulation encoding the signal in apre-set manner to record the resulting modulation-coded signal.

A modulation-coder, performing this modulation coding, routinely is fedwith binary signals exempt from various limitations, and outputs binarysignals free of various limitations. These limitations on the signalsinclude DC free limitations which state that the numbers of “0”s and“1”s be equalized over a sufficient long length of the concatenations of“0”s and “1”s, and the (d, k) limitations which state that the minimumand maximum numbers of consecutive “0”s and “1”s in a code be d and k,respectively. FIG. 1 shows an input/output example in a modulation coderoutputting a code satisfying the (d, k)=(2, 7) limitations.Specifically, a modulation coder 150, outputting a code satisfying the(d, k)=(2, 7) limitation, is shown in FIG. 1, by way of concreteexplanation of the concept of the (d, k) limitations. That is, if aninput signal, free of the limitation, is input to the modulation coder150, outputting a code satisfying the (d, k)=(2, 7) limitation,modulation-encodes the input signal to generate and output an outputsignal in which the minimum and maximum numbers of consecutive “0”s are2 and 7, respectively.

The above example indicates that, in converting a bit string free of alimitation is converted into another bit string subjected to alimitation, the total number of the output bits is larger than that ofthe input bits. If the total number of input bits is K and the totalnumber of output bits is N, the ratio K/N is represented as a code rateR. This code rate R serves as an index indicating the efficiency of themodulation coding. If two or more modulation coders, generating outputsignals satisfying the same limitations, are compared to one another, amodulation coder having the high code rate R is able to encode moreinput bits for a given number of output bits than one having the lowcode rate R. Stated differently, a modulation coder having a high coderate R is able to record more information on a pre-set recording mediumthan one having a low code rate R.

The modulation coding may be classified into a block coding system inwhich input bits are divided into plural blocks of pre-set lengths andoutput bits generated are divided into plural blocks of pre-set lengthscorresponding to the blocks of the input bits, and a variable lengthcoding system, in which encoding units of input bits and output bitsassociated with the input bits are varied. For example, the so-called8/9 code or the 16/17 code, routinely used for modulation coding, belongto the block coding system, whilst the so-called (1, 7) RLL code or the(2, 7) RLL code belong to the variable length encoding system.

For example, in a block modulation encoding system, fed with two bits asinput bits, and generating three output bits satisfying the (d, k)=(0,2) limitations, a modulation coder has a conversion table as Table 1:

TABLE 1 Example of Conversion Table input bits output bits 00 011 01 10110 111 11 110stored in e.g., a memory, not shown. The modulation coder referencesthis conversion table and finds, for each 2-bit input bits, anassociated 3-bit output bits, with the output bits being issued asoutput sequentially.

On the other hand, a modulation decoder for modulating-decoding themodulation-coded signals has a back-conversion table, as Table 2:

TABLE 2 Example of Back-Conversion Table input bit decoded bits 000 01001 00 010 10 011 00 100 11 101 01 110 11 111 10corresponding to the conversion table of Table 1, stored in e.g., amemory, not shown. The modulation decoder references thisback-conversion table to find and sequentially output 2-bit decodedbits, associated with the 3-bit input bits.

FIG. 2 shows a typical modulation decoder 160 having at least a ROM(read-only memory) 161. The modulation decoder 160 is fed with an inputaddress signal D161 to output the contents stored in an address of theROM 161 corresponding to this input address signal D161 as a demodulateddecoded signal D162. In actuality, if the input bits are back-convertedinto decoded bits in accordance with the back-conversion table shown inTable 2, the contents of the decoded bits are stored in addresses of aROM 161 of the modulation decoder 160, corresponding to the input bitsin Table 2. The decoded bits, stored in these addresses, are read out byway of performing the back-conversion.

FIG. 3 shows a typical modulation decoder 170 at least having acombination circuit 171. The modulation decoder 170 is fed with an inputsignal D171 and executes logical operations on the input signal D171 bythe combination circuit 171 to generate a modulated decoded signal D172.In actuality, if, in performing back conversion from the input bits tothe decoded bits in accordance with the back-conversion table of Table2, the three-bit input signal D171 is represented as (a₀, a₁, a₂) and atwo-bit modulated decoded signal D172 is represented as (b₀, b₁), themodulation decoder 170 generates the output bits (b₀, b₁) by thecombination circuit 171 corresponding to the following logical equations(1):b ₀=(a ₁&a ₂)|(a ₀&!a ₁&!a ₂)|(!a ₀&a ₁&!a ₂)b ₁=(a ₀&!a ₁)|(!a ₀&!a ₁&!a ₂)|(a ₀&a ₁&!a ₂)  (1)where |, & and ! indicate the logical sum, logical product and logicalnegation, respectively.

If the modulation coder and the modulation decoder are applied to amagnetic recording and/or reproducing apparatus for recording and/orreproducing data on or from a recording medium in accordance with themagnetic recording system, the recording and/or reproducing apparatus isconfigured as shown in FIG. 4.

That is, the magnetic recording and/or reproducing apparatus 200, shownin FIG. 4, includes, as a recording system for recording data on arecording medium 250, an error correction encoder 201 for errorcorrection encoding input data, a modulation encoder 201, a modulationencoder 202 for modulation encoding the input data, a precoder 203 forfiltering input data for compensating its channel characteristics, awrite current driver 204 for converting respective bits of the inputdata into write current values, and a write head 205 for recording dataon the recording medium 250. The magnetic recording and/or reproducingapparatus 200 also includes, as a playback system for reproducing datarecorded on the recording medium 250, a readout head 206 for reading outdata recording on the recording medium 250, an equalizer 207 forequalizing the input data, a gain adjustment circuit 208 for adjustingthe gain of the input data, an analog/digital converter (A/D converter)209 for converting analog data into digital data, a timing generatingcircuit 210 for generating clocks, a gain adjustment control circuit 211for controlling the gain adjustment circuit 208, a viterbi decoder 212for viterbi-decoding the input bits, a modulation decoder 213 formodulation decoding the input data and an error correction decoder 214for error correction decoding the input data.

In recording data on the recording medium 250, the magnetic recordingand/or reproducing apparatus 200 performs the following operations:

When fed with the input data D201 the magnetic recording and/orreproducing apparatus 200 applies error correction coding to the inputdata D201, by the error correction encoder 201, to generate errorcorrection encoded data D202.

The magnetic recording and/or reproducing apparatus 200 modulationencodes the error correction encoded data D202 from the error correctionencoder 201, by the modulation encoder 202, to generatemodulation-encoded data D203, which is a string of bits subjected tolimitations.

The magnetic recording and/or reproducing apparatus 200 performsfiltering on the modulation-encoded data D203, supplied from themodulation encoder 202, by the precoder 203, in such a manner as tocompensate for the channel characteristics as from the writing of dataon the recording medium 250 up to outputting thereof at an equalizer 207in the reproducing system, to generate a precode signal D204. Forexample, if the channel has 1−D characteristics, the precoder 203performs the filtering F indicated by the following equation (2):F=1/(1⊕D)  (2)where ⊕ denotes exclusive-OR.

The magnetic recording and/or reproducing apparatus 200 then convertsrespective bits of the precode signal D204, as binary signal suppliedfrom the precoder 203, by a write current driver 204, into write currentvalues Is, such as by 0→−I_(S), 1→+I_(S), to generate a write currentsignal D205.

By the write head 205, the magnetic recording and/or reproducingapparatus 200 applies a magnetic write signal D206, corresponding to thewrite current signal D205 supplied from the write current driver 204, tothe recording medium 250.

By the above processing, the magnetic recording and/or reproducingapparatus 200 is able to record data on the recording medium 250.

In reproducing the data recorded on the recording medium 250, themagnetic recording and/or reproducing apparatus 200 performs thefollowing processing:

First, the magnetic recording and/or reproducing apparatus 200 reads outthe. readout magnetization signal D207 from the recording medium 250 bythe readout head 206 to generate a readout current signal D208conforming to this readout magnetization signal D207.

The magnetic recording and/or reproducing apparatus 200 then equalizesthe readout current signal D208, supplied from the readout head 206, bythe equalizer 207, so that the channel response since data writing onthe recording medium 250 in the recording system until outputtingthereof at the equalizer 207 will be of pre-set characteristics, such as1−D, to generate an equalized signal D209.

The magnetic recording and/or reproducing apparatus 200 then adjusts thegain of the equalized signal D209, supplied from the equalizer 207, bythe gain adjustment circuit 208, based on a gain adjustment controlsignal D213 from the gain adjustment control circuit 211, to generate again adjustment signal D210. Meanwhile, the gain adjustment controlsignal D213 is generated by the gain adjustment control circuit 211,based on the digital channel signal D211, as later explained.Specifically, the gain adjustment control signal D213 is a controlsignal for maintaining the amplitude of the equalization signal D209 atan expected value.

By the A/D converter 209, the magnetic recording and/or reproducingapparatus 200 digitizes the gain adjustment signal D210, supplied fromthe gain adjustment circuit 208, to generate the digital channel signalD211. Meanwhile, the A/D converter 209 performs sampling based on theclock signal D212 generated and supplied by the timing generatingcircuit 210. The timing generating circuit 210, fed with the digitalchannel signal D211, generates clocks to produce clock signals D212which are output to the A/D converter 209.

The magnetic recording and/or reproducing apparatus 200 feeds thedigital channel signal D211, supplied from the A/D converter 209, to theviterbi decoder 212, which then performs viterbi decoding on the channelresponse from the upstream side of the precoder 203 in the recordingsystem up to the outputting at the equalizer 207 in the reproducingsystem, for example, the channel response R_(ch) represented by thefollowing equation (3):R _(ch)=(1−D)/(1⊕D)  (3)where ⊕ denotes Exclusive-OR.

The magnetic recording and/or reproducing apparatus 200 then appliesmodulation decoding on the viterbi decoded signal D214, supplied fromthe modulation decoder 213, to realize data correspondence reversed fromthat in the modulation encoder 202 in the recording system to generate amodulated decoded signal D215 which is an original input data string notsubjected to limitations.

The magnetic recording and/or reproducing apparatus 200 decodes theerror correction codes of the modulated decoded signal D215, suppliedfrom the modulation decoder 213, by the error correction decoder 214, togenerate output data D216.

By the above processing, the magnetic recording and/or reproducingapparatus 200 is able to reproduce the data recorded on the recordingmedium 250.

Meanwhile, in the above-described conventional magnetic recording and/orreproducing apparatus 200, the modulation decoder 213 has no more thanthe function of realizing the correspondence between binary signalsreversed from that obtained on modulation encoding by the modulationencoder 202, while the signals in both the input and the output of themodulation decoder 213 needs to be binary signals, with the result thatthe signals on the downstream side of the viterbi decoder 212 are allbinary signals.

In other words, it is necessary in the magnetic recording and/orreproducing apparatus 200 to generate binary signals on the upstreamside of the modulation decoder 213 and to process the binary signalseven on the downstream side of the modulation decoder 213.

Thus, in the magnetic recording and/or reproducing apparatus 200, inwhich bi-level binary signals need to be used, the information volume inthe signal is diminished intentionally with the result that efficientdecoding cannot be realized to deteriorate the decoding error rate.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodand apparatus for recording data in which high performance encoding maybe carried out to cause the reproducing system to perform highlyefficient decoding operation to lower the decoding error ratesignificantly.

It is another object of the present invention to provide a datareproducing method and apparatus for performing efficient decoding tolower the decoding error rate.

It is yet another object of the present invention to provide a datarecording and reproducing method and apparatus for realizing highperformance encoding and high efficiency decoding to lower the decodingerror rate.

In one aspect, the present invention provides a data recording apparatusfor recording data on a recording medium, including modulation encodingmeans for applying predetermined modulation encoding to input data, andinterleaving means for interleaving data supplied from the modulationencoding means for re-arraying the data sequence.

In the data recording apparatus, according to the present invention,data supplied from the modulation encoding means is interleaved by theinterleaving means for re-arraying the data sequence, thereby realizinghigh performance encoding.

In another aspect, the present invention provides a data recordingmethod for recording data on a recording medium, including a modulationencoding step of applying predetermined modulation encoding to inputdata, and a interleaving step of interleaving data supplied from themodulation encoding step for re-arraying the data sequence.

In the data recording method, according to the present invention, datasupplied from the modulation encoding step is interleaved in theinterleaving step for re-arraying the data sequence for realizing highperformance encoding.

In another aspect, the present invention provides a data reproducingapparatus for reproducing data recorded by a recording equipment forrecording data on a recording medium, including modulation encodingmeans for applying predetermined modulation encoding to input data andfirst interleaving means for interleaving data supplied from themodulation encoding means for re-arraying the data sequence, in whichthe data reproduction apparatus includes deinterleaving means forinterleaving the input data in its sequence such as to restore thesequence of data bits re-arrayed by the first interleaving means to thebit sequence of the data as encoded by the modulation encoding means,modulation decoding means for modulation decoding the data supplied fromthe deinterleaving means, and second interleaving means for interleavingdata corresponding to a difference between data output by the modulationdecoding means and data output by the deinterleaving means based on thesame interleaving position information as that of the first interleavingmeans for re-arraying the sequence of the difference data.

In such data reproducing apparatus, according to the present invention,the data re-arrayed in its sequence interleaved by the deinterleavingmeans is modulation decoded by the modulation decoding means, whilstdata corresponding to the difference between data output by themodulation decoding means and data output by the deinterleaving means isinterleaved by the second interleaving means for re-arraying thesequence of the different data, whereby efficient decoding can berealized by exploiting the soft information for the entire decodingprocessing to lower the decoding error rate appreciably.

In still another aspect, the present invention provides a datareproducing method for reproducing data recorded by a recording methodfor recording data on a recording medium, including a modulationencoding step for applying predetermined modulation encoding to inputdata and a first interleaving step of interleaving data encoded in themodulation encoding step for re-arraying the data sequence, in which thedata reproduction method includes a deinterleaving step of interleavingthe input data in its sequence such as to restore the sequence of databits re-arrayed by the first interleaving step to the bit sequence ofthe data as encoded by the modulation encoding step, a modulationdecoding step of modulation decoding the data supplied from thedeinterleaving step and a second interleaving step of interleaving datacorresponding to a difference between data decoded in the modulationdecoding step and data re-arrayed in the deinterleaving step based onthe same interleaving position information as that of the firstinterleaving step for re-arraying the sequence of the difference data.

In such data reproducing method, according to the present invention, thedata re-arrayed in its sequence interleaved by the deinterleaving meansis modulation decoded in the modulation decoding step, whilst datacorresponding to the difference between data output by the modulationdecoding step and data output by the deinterleaving step is interleavedby the second interleaving step for re-arraying the sequence of thedifferent data, whereby efficient decoding can be realized by exploitingthe soft information for the entire decoding processing to lower thedecoding error rate appreciably.

In still another aspect, the present invention provides a data recordingand reproducing apparatus for recording and reproducing data for arecording medium, in which the apparatus includes, as a recording systemfor recording data on the recording medium, modulation encoding meansfor applying predetermined modulation encoding to input data, and firstinterleaving means for interleaving data supplied from the modulationencoding means for re-arraying the data sequence, and in which theapparatus also includes, as a reproducing system for reproducing datarecorded on the recording medium, deinterleaving means for interleavingthe input data in its sequence such as to restore the sequence of databits re-arrayed by the first interleaving means to the bit sequence ofthe data as encoded by the modulation encoding means, modulationdecoding means for modulation decoding the data supplied from thedeinterleaving means, and second interleaving means for interleavingdata corresponding to a difference between data output by the modulationdecoding means and data output by the deinterleaving means based on thesame interleaving position information as that of the first interleavingmeans for re-arraying the sequence of the difference data.

In the data recording and reproducing apparatus, according to thepresent invention, if data is to be recorded on a recording medium, thedata supplied from the modulation encoding means is interleaved by firstinterleaving means to re-array the data sequence, whereas, if datarecorded on the recording medium is to be reproduced, data given as adifference between second interleaving means for interleaving datacorresponding to a difference between data output by the modulationdecoding means and data output by the deinterleaving means based on thesame interleaving position information as that of said firstinterleaving means is interleaved and re-arrayed, so that highperformance encoding may be achieved, at the same time as efficientdecoding may be achieved by exploiting the soft information for theentire decoding for the code, thus significantly lowering the decodingerror rate.

In yet another aspect, the present invention provides a data recordingand reproducing method for recording and reproducing data for arecording medium, in which the method includes, as a recording systemfor recording data on the recording medium, a modulation encoding stepfor applying predetermined modulation encoding to input data, and afirst interleaving step for interleaving data supplied from themodulation encoding step for re-arraying the data sequence, and in whichthe method also includes, as a reproducing system for reproducing datarecorded on the recording medium, a deinterleaving step for interleavingthe input data in its sequence such as to restore the sequence of databits re-arrayed by the first interleaving step to the bit sequence ofthe data as encoded by the modulation encoding step, a modulationdecoding step for modulation decoding the data supplied from thedeinterleaving step, and a second interleaving step for interleavingdata corresponding to a difference between data decoded in themodulation decoding step and data re-arrayed in the deinterleaving stepbased on the same interleaving position information as that of the firstinterleaving step for re-arraying the sequence of the difference data.

In the data recording and reproducing method, according to the presentinvention, if data is to be recorded on a recording medium, the datasupplied from the modulation encoding step is interleaved by the firstinterleaving step to re-array the data sequence, whereas, if datarecorded on the recording medium is to be reproduced, data given as adifference between second interleaving means for interleaving datacorresponding to a difference between data output by the modulationdecoding means and data output by the deinterleaving means based on thesame interleaving position information as that of said firstinterleaving means is interleaved and re-arrayed, so that highperformance encoding may be achieved, at the same time as efficientdecoding may be achieved by exploiting the soft information for theentire decoding for the code, thus significantly lowering the decodingerror rate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an input/output example of a conventional modulationencoder.

FIG. 2 is a block diagram showing the structure of a conventionalmodulation decoder.

FIG. 3 is a block diagram showing the structure of another conventionalmodulation decoder.

FIG. 4 is a block diagram showing the structure of a conventionalmagnetic recording and/or reproducing apparatus.

FIG. 5 illustrates an input/output example in an interleaver applied toa recording system of a magnetic recording and/or reproducing apparatusshown as a first embodiment of the present invention.

FIG. 6 illustrates the operation of an interleaver used in a recordingsystem of the magnetic recording and/or reproducing apparatus shown inFIG. 5.

FIG. 7 illustrates an input/output example in a decoder applied to areproducing system of the magnetic recording and/or reproducingapparatus shown in FIG. 5.

FIG. 8 is a block diagram for illustrating the structure of a decoderused in the reproducing system of the magnetic recording and/orreproducing apparatus shown in FIG. 5.

FIG. 9 is a block diagram for illustrating the structure of therecording and/or reproducing apparatus shown in FIG. 5.

FIG. 10 is a block diagram for illustrating the structure of a channeland a modulation turbo decoder provided in the reproducing system of therecording and/or reproducing apparatus shown in FIG. 5.

FIG. 11 illustrates the status transition diagram for generating codessatisfying the (d, k)=(0, 2) limitations.

FIG. 12 illustrates the trellis when status transition has occurredthrice in accordance with the status transition diagram shown in FIG.11.

FIG. 13 illustrates the trellis constructed on branch selection from thetrellis shown in FIG. 12.

FIG. 14 is a block diagram showing the structure of an encoder used in arecording system of a magnetic recording and/or reproducing apparatusshown as a second embodiment of the present invention.

FIG. 15 is a block diagram for illustrating the structure of themagnetic recording and/or reproducing apparatus.

FIG. 16 is a block diagram for illustrating the structure of the channeland a modulation turbo decoder provided in a reproducing system of themagnetic recording and/or reproducing apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, preferred embodiments of the presentinvention will be explained in detail.

The present embodiment is directed to a magnetic recording and/orreproducing apparatus made up of a recording system for recording dataon a recording medium of the magnetic recording system, such as a harddisc or a so-called DVCR (digital video cassette recorder), and areproducing system for reproducing data recorded on these recordingmediums.

This magnetic recording and/or reproducing apparatus includes, in itsrecording system, an interleaver downstream of a modulation encoder,adapted for modulating signals, and executes encoding by so-calledserial concatenated coding between a modulation encoder and a precoder,adapted for performing filtering on signals, in such a manner as tocompensate for channel characteristics. Moreover, the magnetic recordingand/or reproducing apparatus uses, on the reproducing side, a decoderfor the channel and a decoder for modulation decoding the modulationencoded signals, that is an SISO (soft input soft output) type decoder,fed with soft input data to output soft output data, and iterativelyexecutes decoding between these two decoders. This decoding is termedturbo decoding. That is, the magnetic recording and/or reproducingapparatus applies the encoding by the serial concatenated code and turbodecoding, known as the encoding method and decoding method giving theperformance close to the Shannon limit as set by what is called theShannon's theorem on the channel coding, to a recording and/orreproducing system performing data recording and/or reproduction for arecording medium.

First, the magnetic recording and/or reproducing apparatus as a firstembodiment is explained. Here, the interleaver, applied to the recordingsystem of this magnetic recording and/or reproducing apparatus, isexplained by referring to FIGS. 5 and 6.

An interleaver 10, shown in FIG. 5, interleaves data, encoded by blockmodulation by a modulation encoder provided on a pre-stage of theinterleaver 10, on the modulation code block basis, that is on thesymbol basis, to re-array the bits making up the data. For example, ifthe interleaver 10 re-arrays respective bits of data modulation-encodedto generate 3 output bits for 2 input bits in accordance with aconversion table shown in the following Table 3, the interleaver 10re-arrays an input signal, fed in a unit of three bits, as a modulationencoder block unit, in a unit of three bits, as shown in FIG. 6, togenerate an output signal:

TABLE 3 Example of Conversion Table input bits output bits 00 011 01 10110 111 11 110

More specifically, the interleaver 10 holds the interleaving positioninformation of data determined on the basis of generated random numbersin e.g., a ROM (read-only memory), and re-arrays the input signal on themodulation code block basis, based on the interleaving positioninformation. For example, the interleaver 10 holds the interleavingposition information of data making up an input signal, and re-arraysthe bits on the modulation encoding block basis, in accordance with theinterleaving position information, at a timing of generation of the bitstring made up of N bits, where N is an optional natural number, tooutput the re-arrayed bits as an output signal at a preset timing.

The decoder for modulation-decoding the modulation encoded signals, as aSISO type decoder applied to the reproducing system of the magneticrecording and/or reproducing apparatus, is explained with reference toFIGS. 7 and 8. It should be noted that, although the decoders 20, 30,shown in FIGS. 7 and 8, are shown as being the decoders formodulation-decoding the modulation-encoded signals, the decoder for thechannel is to be realized in a similar manner.

A decoder 20, shown in FIG. 7, decodes data encoded by block modulation,with the code rate R=k/n, where k is the number of input bits and n isthe number of bits for modulation coding.

When fed with a reception signal R as the soft input, the decoder 20calculates the probability P (R_(i)=0|R) that the respective bits ofthis reception signal R are each “0” and the probability P (R_(i)=1|R)that the respective bits of this reception signal R are each “1”.Ultimately, the decoder 20 calculates a posterior probabilityinformation P (M_(i)=0|R) and P (M_(i)=1|R), as a soft decision valuefor a modulation code block M represented by M=(M₀, M₁, . . . ,M_(n−1)), and/or a posterior probability information P (C_(i)=0|R) and P(C_(i)=1|R), as a soft decision value for a modulation code input blockC represented by C=(C₀, C₁, . . . , C_(k−1)), to output theso-calculated information.

Instead of individually outputting the aforementioned posteriorprobability information, the decoder is also able to output thelogarithmic value of the ratio of the posterior probability information,that is log(P(M_(i)=1|R)/P(M_(i)=0|R)) orlog(P(C_(i)=1|R)/P(C_(i)=0|R)). These log values are routinely termedthe log likelihood ratio and here denote the likelihood of themodulating code block M and the modulating code input block C on theoccasion of inputting the reception signal R.

The decoder may also be fed with the priori probability information P(C_(i)=0) and P (C_(i)=1) for a modulation code input block C, insteadof being fed with the aforementioned reception signal R.

Specifically, the decoder may, for example, be configured as shown inFIG. 8. In the following explanation, it is assumed that, for generatinga three-bit output for a two-bit input, data to be decoded has beenencoded in accordance with the conversion table shown in Table 3 givenabove.

The modulation decoder 30, shown in FIG. 8, includes six likelihoodcalculating circuits 31 ₁, 31 ₂, 31 ₃, 31 ₄, 31 ₅ and 31 ₆, as means forcalculating the likelihood of each reception bit, four adders 32 ₁, 32₂, 32 ₃ and 32 ₄ for summing the data, four log-sum circuits 33 ₁, 33 ₂,33 ₃ and 33 ₄ for performing the operations of log (e^(A)+e^(B)) on thetwo data A and B, four adders 34 ₁, 34 ₂, 34 ₃ and 34 ₄ for summing twodata, five comparators 35 ₁, 35 ₂, 36 ₁, 36 ₂ and 36 ₃ for taking theratio of the two data, coefficient calculating circuits 37 ₁, 37 ₂ and37 ₃ for calculating coefficients for respective elements in themodulation encoding block M and three adders 38 ₁, 38 ₂ and 38 ₃ foradding two data. It is noted that the number six of the likelihoodcalculating circuits is derived from three bits multiplied by 2 equalsto six bits.

The likelihood calculating circuits 31 ₁, 31 ₂, 31 ₃, 31 ₄, 31 ₅ and 31₆ are respectively fed with respective reception bits in a receptionsignal D31 (R) to calculate the likelihood of the respective receptionbits.

That is, the likelihood calculating circuits 31 ₁ is fed with the 0thbit of the three-bit reception signal D31 to calculate the logprobability value D32 ₁ (log P(R₀=0|R)) corresponding to the log valueof the probability that this bit is “0”. The likelihood calculatingcircuits 31 ₁ sends the generated log probability value D32 ₁ to theadder 32 ₁.

The likelihood calculating circuits 31 ₂ is fed with the 0th bit of thethree-bit reception signal D31 to calculate the log probability valueD32 ₂ (log P(R₀=1|R)) corresponding to the log value of the probabilitythat this bit is “1”. The likelihood calculating circuits 31 ₂ sends thegenerated log probability value D32 ₂ to the adders 32 ₂, 32 ₃ and 32 ₄and to the comparator 36 ₁.

Then, the likelihood calculating circuits 31 ₃ is fed with the first bitof the three-bit reception signal D31 to calculate the log probabilityvalue D32 ₃ (log P(R₁=0|R)) corresponding to the log value of theprobability that this bit is “0”. The likelihood calculating circuits 31₃ sends the generated log probability value D32 ₃ to the adder 32 ₂ andto the comparator 36 ₂.

The likelihood calculating circuits 31 ₄ is fed with the first bit ofthe three-bit reception signal D31 to calculate the log probabilityvalue D32 ₄ (log P(R₁=1|R)) corresponding to the log value of theprobability that this bit is “1”. The likelihood calculating circuits 31₄ sends the generated log probability value D32 ₄ to the adder 32 ₁, 32₃ and 32 ₄ and to the comparator 36 ₂.

Then, the likelihood calculating circuits 31 ₅ is fed with the secondbit of the three-bit reception signal D31 to calculate the logprobability value D32 ₅ (log P(R₂=0|R)) corresponding to the log valueof the probability that this bit is “0”. The likelihood calculatingcircuits 31 ₅ sends the generated log probability value D32 ₅ to theadder 32 ₄ and to the comparator 36 ₃.

The likelihood calculating circuits 31 ₆ is fed with the second bit ofthe three-bit reception signal D31 to calculate the log probabilityvalue D32 ₆ (log P(R₂=1|R)) corresponding to the log value of theprobability that this bit is “1”. The likelihood calculating circuits 31₆ sends the generated log probability value D32 ₆ to the adders 32 ₁, 32₂ and 32 ₃ and to the comparator 36 ₃.

The adder D32 ₁ sums the log probability value D32 ₁, supplied from thelikelihood calculating circuits 31 ₁, the log probability value D32 ₄,supplied from the likelihood calculating circuits 31 ₄ and the logprobability value D32 ₆, supplied from the likelihood calculatingcircuits 31 ₆, to generate the likelihood value D33 ₁. That is, thislikelihood value D33 ₁ is not other than the probability represented bylog P(R|M₀M₁M₂=011). The adder D32 ₁ sends the generated likelihoodvalue D33 ₁ to the log-sum circuits 33 ₁, 33 ₃.

The adder D32 ₂ sums the log probability value D32 ₂, supplied from thelikelihood calculating circuits 31 ₂, the log probability value D32 ₃,supplied from the likelihood calculating circuits 31 ₃ and the logprobability value D32 ₆, supplied from the likelihood calculatingcircuits 31 ₆ to generate the likelihood value D33 ₂. That is, thislikelihood value D33 ₂ is not other than the probability represented bylog P(R|M₀M₁M₂=101). The adder D32 ₂ sends the generated likelihoodvalue D33 ₂ to the log-sum circuits 33 ₁, 33 ₄.

The adder D32 ₃ sums the log probability value D32 ₂, supplied from thelikelihood calculating circuits 31 ₂, the log probability value D32 ₄,supplied from the likelihood calculating circuits 31 ₄, and the logprobability value D32 ₆, supplied from the likelihood calculatingcircuits 31 ₆, to generate the likelihood value D33 ₃. That is, thislikelihood value D33 ₃ is not other than the probability represented bylog P(R|M₀M₁M₂=111). The adder D32 ₃ sends the generated likelihoodvalue D33 ₃ to the log-sum circuits 33 ₂, 33 ₃.

The adder D32 ₄ sums the log probability value D32 ₂, supplied from thelikelihood calculating circuits 31 ₂, the log probability value D32 ₄,supplied from the likelihood calculating circuits 31 ₄ and the logprobability value D32 ₅, supplied from the likelihood calculatingcircuits 31 ₅, to generate the likelihood value D33 ₄. That is, thislikelihood value D33 ₄ is not other than the probability represented bylog P(R|M₀M₁M₂=110). The adder D32 ₄ sends the generated likelihoodvalue D33 ₄ to the log-sum circuits 33 ₂, 33 ₄.

The log-sum circuit 33 ₁ performs an operation shown by the equation(4):log(e ^(log P(R|M) ⁰ ^(M) ¹ ^(M) ² ⁼⁰¹¹⁾ +e ^(log P(R|M) ⁰ ^(M) ¹ ^(M) ²⁼¹⁰¹⁾)=log(P(R|M ₀ M ₁ M ₂=011)+P(R|M ₀ M ₁ M ₂=101))  (4)on the likelihood value D33 ₁ supplied from the adder 32 ₁ and on thelikelihood value D33 ₂ supplied from the adder 32 ₂ to generate alikelihood value D34 ₁. The log-sum circuit 33 ₁ sends the so-generatedlikelihood value D34 ₁ to the adder 34 ₁.

The log-sum circuit 33 ₂ performs an operation shown by the equation(5):log(e ^(log P(R|M) ⁰ ^(M) ¹ ^(M) ² ⁼¹¹¹⁾ +e ^(log P(R|M) ⁰ ^(M) ¹ ^(M) ²⁼¹¹⁰⁾)=log(P(R|M ₀ M ₁ M ₂=111)+P(R|M ₀ M ₁ M ₂=110))  (5)on the likelihood value D33 ₃ supplied from the adder 32 ₃ and on thelikelihood value D33 ₄ supplied from the adder 32 ₄ to generate alikelihood value D34 ₂. The log-sum circuit 33 ₂ sends the so-generatedlikelihood value D34 ₂ to the adder 34 ₂.

The log-sum circuit 33 ₃ performs an operation shown by the equation(6):log(e ^(log P(R|M) ⁰ ^(M) ¹ ^(M) ² ⁼⁰¹¹⁾ +e ^(log P(R|M) ⁰ ^(M) ¹ ^(M) ²⁼¹¹¹⁾)=log(P(R|M ₀ M ₁ M ₂=011)+P(R|M ₀ M ₁ M ₂=111))  (6)on the likelihood value D33 ₁ supplied from the adder 32 ₁ and on thelikelihood value D33 ₃ supplied from the adder 32 ₃ to generate alikelihood value D34 ₃. The log-sum circuit 33 ₃ sends the so-generatedlikelihood value D34 ₃ to the adder 34 ₃.

The log-sum circuit 33 ₄ performs an operation shown by the equation(7):log(e ^(log P(R|M) ⁰ ^(M) ¹ ^(M) ² ⁼¹⁰¹⁾ +e ^(log P(R|M) ⁰ ^(M) ¹ ^(M) ²⁼¹¹⁰⁾)=log(P(R|M ₀ M ₁ M ₂=101)+P(R|M ₀ M ₁ M ₂=110))  (7)on the likelihood value D33 ₂ supplied from the adder 32 ₂ and on thelikelihood value D33 ₄ supplied from the adder 32 ₄ to generate alikelihood value D34 ₄. The log-sum circuit 33 ₄ sends the so-generatedlikelihood value D34 ₄ to the adder 34 ₄.

The adder 34 ₁ sums the likelihood value D34 ₁ supplied from the log-sumcircuit 33 ₁ and the log priori probability D35 ₁ (log P(C₀=0)) for aninput bit, fed from outside, to generate the log probability value D36₁. This log probability value D36 ₁ denotes the probability shown by thefollowing equation (8):log P(C ₀=0|R)=log {P(R|M ₀ M ₁ M ₂=011)+(R|M ₀ M ₁ M ₂=101)}+logP(C₀=0)  (8).The adder 34 ₁ sends the generated log probability value D36 ₁ to acomparator 35 ₁.

The adder 34 ₂ sums the likelihood value D34 ₂ supplied from the log-sumcircuit 33 ₂ and the log priori probability D35 ₂ (log P(C₀=1)) for aninput bit, input from outside, to generate the log probability value D36₂. This log probability value D36 ₂ denotes the probability shown by thefollowing equation (9):log P(C ₀=1|R)=log {P(R|M ₀ M ₁ M ₂=111)+(R|M ₀ M ₁ M ₂=110)}+log P(C₀=1)  (9).The adder 34 ₂ sends the generated log probability value D36 ₂ to acomparator 35 ₁.

The adder 34 ₃ sums the likelihood value D34 ₃ supplied from the log-sumcircuit 33 ₃ and the log priori probability D35 ₃ (log P(C₁=0)) for aninput bit, input from outside, to generate the log probability value D36₃. This log probability value D36 ₃ denotes the probability shown by thefollowing equation (10):log P(C ₁=0|R)=log {P(R|M ₀ M ₁ M ₂=011)+(R|M ₀ M ₁ M ₂=111)}+log P(C₁=0)  (10).The adder 34 ₃ sends the generated log probability value D36 ₃ to thecomparator 35 ₂.

The adder 34 ₄ sums the likelihood value D34 ₄ supplied from the log-sumcircuit 33 ₄ and the log priori probability D35 ₄ (log P(C₁=1)) for aninput bit, input from outside, to generate the log probability value D36₄. This log probability value D36 ₄ denotes the probability shown by thefollowing equation (11):log P(C ₁=1|R)=log {P(R|M ₀ M ₁ M ₂=101)+(R|M ₀ M ₁ M ₂=110)}+log P(C₁=1)  (11).The adder 34 ₄ sends the generated log probability value D36 ₄ to acomparator 35 ₂.

The comparator 35 ₁ takes the ratio of the log probability value D36 ₁supplied from the adder 34 ₁ and the log probability value D36 ₂supplied from the adder 34 ₂ to generate the decoded log posteriorprobability ratio D37 ₁ (log(P(C₀=1|R)/P(C₀=0|R))) which is output tooutside.

The comparator 35 ₂ takes the ratio of the log probability value D36 ₃supplied from the adder 34 ₃ and the log probability value D36 ₄supplied from the adder 34 ₄ to generate the decoded log posteriorprobability ratio D37 ₂ (log(P(C₁=1|R)/P(C₁=0|R))) which is output tooutside.

The comparator 36 ₁ takes the ratio of the log probability value D32 ₁supplied from the likelihood calculating circuit 31 ₁ and the logprobability value D32 ₂ supplied from the likelihood calculating circuit31 ₂ to generate the log posterior probability ratio D38 ₁(log(P(M₀=1|R)/P(M₀=0|R))) which is output to the adder 38 ₁.

The comparator 36 ₂ takes the ratio of the log probability value D32 ₃supplied from the likelihood calculating circuit 31 ₃ and the logprobability value D32 ₄ supplied from the likelihood calculating circuit31 ₄ to generate the log posterior probability ratio D38 ₂(log(P(M₁=1|R)/P(M₁=0|R))) which is output to the adder 38 ₂.

The comparator 36 ₃ takes the ratio of the log probability value D32 ₅supplied from the likelihood calculating circuit 31 ₅ and the logprobability value D32 ₆ supplied from the likelihood calculating circuit31 ₆ to generate the log posterior probability ratio D38 ₃(log(P(M₂=1|R)/P(M₂=0|R))) which is output to the adder 38 ₃.

The coefficient calculating circuit 37 ₁ calculates the M₀ coefficient,represented by the following equation (12):

$\begin{matrix}{\alpha = {\log\mspace{11mu}\frac{{P{( {C_{0} = 0} ) \cdot {P( {C_{1} = 1} )}}} + {{P( {C_{0} = 1} )} \cdot {P( {C_{1} = 0} )}} + {{P( {C_{0} = 1} )} \cdot {P( {C_{1} = 1} )}}}{{P( {C_{0} = 0} )} \cdot {P( {C_{1} = 0} )}}}} & (12)\end{matrix}$that is a coefficient α for the modulation code M₀ equivalent to the 0thbit making up the three-bit reception signal D31, based on the logpriori probability D35 ₁, D35 ₂, D35 ₃ and D35 ₄ for the input bitsupplied from outside, to generate a M₀ coefficient signal D39 ₁. Thecoefficient calculating circuit 37 ₁ sends the generated M₀ coefficientD39 ₁ to the adder 38 ₁.

The coefficient calculating circuit 37 ₂ calculates the M₁ coefficient,represented by the following equation (13):

$\begin{matrix}{\beta = {\log\;\frac{{P{( {C_{0} = 0} ) \cdot {P( {C_{1} = 0} )}}} + {{P( {C_{0} = 1} )}{P( {C_{1} = 0} )}} + {{P( {C_{0} = 1} )} \cdot {P( {C_{1} = 1} )}}}{{P( {C_{0} = 1} )} \cdot {P( {C_{1} = 1} )}}}} & (13)\end{matrix}$that is a coefficient β for the modulation code M₁ equivalent to thefirst bit making up the three-bit reception signal D31, based on the logpriori probability D35 ₁, D35 ₂, D35 ₃ and D35 ₄ for the input bitsupplied from outside, to generate a M₁ coefficient signal D39 ₂. Thecoefficient calculating circuit 37 ₂ sends the generated M₁ coefficientD39 ₂ to the adder 38 ₂.

The coefficient calculating circuit 37 ₃ calculates the M₂ coefficient,represented by the following equation (14):

$\begin{matrix}{\gamma = {\log\frac{{P{( {C_{0} = 0} ) \cdot {P( {C_{1} = 0} )}}} + {{P( {C_{0} = 0} )}{P( {C_{1} = 1} )}} + {{P( {C_{0} = 1} )} \cdot {P( {C_{1} = 0} )}}}{{P( {C_{0} = 1} )} \cdot {P( {C_{1} = 1} )}}}} & (14)\end{matrix}$that is a coefficient γ for the modulation code M₂ equivalent to thesecond bit making up the three-bit reception signal D31, based on thelog priori probability D35 ₁, D35 ₂, D35 ₃ and D35 ₄ for the input bitsupplied from outside, to generate a M₂ coefficient signal D39 ₃. Thecoefficient calculating circuit 37 ₃ sends the generated M₂ coefficientD39 ₃ to the adder 38 ₃.

The adder 38 ₁ sums the log posterior probability ratio D38 ₁, suppliedfrom the comparator 36 ₁, to the M₁ coefficient signal D39 ₁ suppliedfrom the coefficient calculating circuit D37 ₁. The adder 38 ₁ outputsthe decoded channel log posterior probability ratio signal D40₁(log(P(M₀=1|R)/P(M₀=0|R))) to outside.

The adder 38 ₂ sums the log posterior probability ratio D38 ₂, suppliedfrom the comparator 36 ₂, to the M₁ coefficient signal D39 ₂ suppliedfrom the coefficient calculating circuit D37 ₂. The adder 38 ₂ outputsthe decoded channel log posterior probability ratio signal D40₂(log(P(M₁=1|R)/P(M₁=0|R))) to outside.

The adder 38 ₃ sums the log posterior probability ratio D38 ₃, suppliedfrom the comparator 36 ₃, to the M₂ coefficient signal D39 ₃ suppliedfrom the coefficient calculating circuit D37 ₃. The adder 38 ₃ outputsthe decoded channel log posterior probability ratio signal D40₃(log(P(M₂=1|R)/P(M₂=0|R))) to outside.

The decoder 30, having the components as described above, has thelikelihood calculating circuits 31 ₁, 31 ₂, 31 ₃, 31 ₄, 31 ₅ and 31 ₆for calculating the likelihood of respective reception bits in thereception signals D31(R) taking analog values under the effect of thenoise generated in the course of transmission, as soft input, that isthe respective output codewords on the modulation coder side. By theselikelihood calculating circuits 31 ₁, 31 ₂, 31 ₃, 31 ₄, 31 ₅ and 31 ₆,the modulation decoder 30 finds the likelihood of the respectivecodewords and uses the likelihood values, thus found, to find theposterior probability information straightforwardly, as soft decisionvalues for the input and output bits on the modulation coder side.

Meanwhile, the decoder 30 is fed from outside with log prioriprobability D35 ₁, D35 ₂, D35 ₃, D35 ₄ If the probability of therespective bits making up the binary signal input to the modulationcoder, not shown, being “0”, is equivalent to the same probability being“1”, there is no necessity of inputting the log priori probability D35₁, D35 ₂, D35 ₃, D35 ₄, it being only necessary to handle as if thevalues of these log priori probability D35 ₁, D35 ₂, D35 ₃, D35 ₄ areall equal to zero.

Although the above explanation is based on the assumption that themodulation decoder 30 decodes data obtained on modulation-coding a 2-bitinput to a 3-bit output, the modulation decoder is not limited as to thenumber of bits of the input or the output and may be similarlyconfigured in keeping with the number of bits of the input or the outputused.

Referring to FIG. 9, the magnetic recording and/or reproducingapparatus, employing this interleaver and decoder, is hereinafterexplained.

A magnetic recording and/or reproducing apparatus 50, shown in FIG. 9,includes, as a recording system for recording data on a recording medium70, an error correction coder 51 for error correction coding input data,a modulation coder 52 for modulation coding input data, an interleaver53 for re-arraying the input data, a precoder 54 for filtering the inputdata for compensating for channel characteristics, a write currentdriver 55 for converting respective bits of the input data into writecurrent values, and a write head 56 for recording data on a recordingmedium 70.

The error correction coder 51, as error correction encoding means,applies error correction coding to the input data D51. The errorcorrection coder 51 sends the error correction encoded data D52,generated on error correction coding, to the downstream side modulationencoder 52.

The modulation encoder 52, as modulation encoding means, appliespredetermined modulation coding to the error correction encoded dataD52, supplied from the error correction coder 51, to generate modulationencoded data D53 as a string subjected to limitations. The modulationencoder 52 sends the so-generated modulation encoded data D53 to thedownstream side interleaver 53.

The interleaver 53, as (first) interleaving means, is constructed as theaforementioned interleaver 10, interleaving the modulation encoded dataD53, encoded with block modulation by the modulation encoder 52, on themodulation encoding block basis, to re-array the sequence of bits makingup the modulation encoded data D53. The interleaver 53 sends thegenerated interleaved data D54 to the downstream side precoder 54.

The precoder 54 as preceding means filters the interleaved data D54,supplied from the interleaver 53, in such a manner as to compensate forchannel characteristics from the data writing to the recording medium 70to the outputting thereof in the equalizer 58 in the reproducing system,thereby generating a precode signal D55 as a binary signal. For example,if the channel has 1−D characteristics the precoder 54 performsfiltering F represented by the following equation (15):F=1/(1⊕D)  (15)where ⊕ denotes exclusive-OR. The precoder 54 sends the generatedprecode signal D55 to the downstream side write current driver 55.

The write current driver 55 converts respective bits of the precodesignal D55, supplied from the precoder 54, into the write current valueI_(S), so that 0 and 1 will be converted to −I_(S) and +I_(S) (0→−I_(S),1→+I_(S)), respectively, to generate a write current signal D56. Thewrite current driver 55 sends the so-generated write current signal D56to the downstream side write head 56.

The write head 56 routes a write magnetic signal D57, conforming to thewrite current signal D56, supplied from the write current driver 55, tothe recording medium 70 to record data thereon.

When recording data on the recording medium 70, the recording system inthis magnetic recording and/or reproducing apparatus 50 applies errorcorrection coding to the input data D51, by the error correction coder51, to produce error correction coded data D52, which then ismodulation-encoded in a predetermined fashion by the modulation coder52. The so-produced modulation encoded data D53 is interleaved by theinterleaver 53 on the modulation encoding block basis to produce precodesignal D55 by the precoder 54.

The recording system records the precode signal D55, generated by theprecoder 54, on the recording medium 70, through the write head 55 andthe write head 56.

The recording system in the magnetic recording and/or reproducingapparatus includes the interleaver 53 downstream of the modulationencoder 52, and executes serial concatenated coding between themodulation encoder 52 and the precoder 54 to realize high performanceencoding as encoding downstream of the error correction coding andencoding for the channel.

On the other hand, the magnetic recording and/or reproducing apparatus50 includes, as a reproducing system for reproducing the data recordedon the recording medium 70, a readout head 57 for reading out datarecorded on the recording medium 70, an equalizer 58 for equalizinginput data, a gain adjustment circuit 59 for adjusting the gain of theinput data, an analog/digital (A/D) converter 60 for converting analogdata into digital data, a timing reproducing circuit 61 for reproducingclocks, a gain adjustment control circuit 62 for controlling the gainadjustment circuit 59, a channel and modulation turbo decoder 63 forapplying turbo soft decoding to the input data, and an error correctingsoft decoder 64 for applying error correcting soft decoding to the inputdata.

The readout head 57 reads out a readout magnetization signal D58 fromthe recording medium and generates a readout current signal D59corresponding to this readout magnetization signal D58. The readout head57 sends the generated readout current signal D59 to the downstream sideequalizer 58.

The equalizer 58 equalizes the readout current signal D59, supplied fromthe readout head 57, so that the channel response from data writing onthe recording medium 70 in the recording system up to outputting thereofin the equalizer 58 will be of pre-set characteristics, such as 1−D, togenerate an equalized signal D60. The equalizer 58 sends the generatedequalized signal D60 to the downstream side gain adjustment circuit 59.

The gain adjustment circuit 59 adjusts the gain of the equalized signalD60, supplied from the equalizer 58, based on the gain adjustmentcontrol signal D64 supplied from the gain adjustment control circuit 62,to generate a gain adjustment signal D61. The gain adjustment circuit 59sends the generated gain adjustment signal D61 to the downstream sideA/D converter 60.

The A/D converter 60 samples the gain adjustment signal D61, suppliedfrom the gain adjustment circuit 59, based on the clock signal D63supplied from the timing generating circuit 61, to digitize the gainadjustment signal D61 to generate a digital channel signal D62. The A/Dconverter 60 sends the so-generated digital channel signal D62 to thetiming generating circuit 61, gain adjustment control circuit 62 and tothe channel and modulation turbo decoder 63.

The timing generating circuit 61 regenerates clocks from the digitalchannel signal D62, supplied from the A/D converter 60, to generateclock signals D63. The timing generating circuit 61 routes the generatedclock signals D63 to the A/D converter 60.

Based on the digital channel signal D62, supplied from the A/D converter60, the gain adjustment control circuit 62 generates a gain adjustmentcontrol signal D64, which is a control signal used for maintaining theamplitude of the equalized signal D60 at an expected value. The gainadjustment control circuit 62 sends the generated gain adjustmentcontrol signal D64 to the gain adjustment circuit 59.

The channel and modulation turbo decoder 63 concatenates SISO decoders,constructed as the above-mentioned decoders 20, 30, to execute turbodecoding. The channel and modulation turbo decoder 63, explained laterin detail, is fed with the digital channel signal D62, supplied from theA/D converter 60, to perform turbo decoding, and routes a so-generatedturbo decoded signal D65 to the post-stage error correcting soft decoder64.

The error correcting soft decoder 64, as error correction soft decodingmeans, applies the so-called BCJR (Bahl, Cocke, Jelinek and Rahiv)algorithm or the SOVA (soft output viterbi algorithm) to the turbodecoded signal D65, supplied from the channel and modulation turbodecoder 63, to output the soft-decoded signal as soft or hard outputdata D66.

The channel and modulation turbo decoder 63 will be explained in detailby referring to FIG. 10.

Referring to FIG. 10, the channel and modulation turbo decoder 63includes a channel SISO decoder 81, as an SISO type decoder for decodingthe channel response from the pre-stage of the precoder 54 in therecording system up to the outputting stage of the equalizer 58 in thereproducing system, a deinterleaver 83 for restoring the sequence of theinput data to the original sequence, a modulation SISO decoder 84, as adecoder of the SISO type for modulation decoding the input data, adeinterleaver 86 for re-arraying the input data, a changeover switch 87for switching the data input as the priori probability information toinformation bits and two difference taking units 82, 85.

The channel SISO decoder 81, as channel decoding means, is constructedas the aforementioned decoders 20, 30, and is an SISO type decoder. Thechannel SISO decoder 81 is fed with the digital channel signal D62, as asoft input supplied from the A/D converter 60, and with the prioriprobability information D78, which is the priori probability informationD76 for an information bit as a soft input supplied from the interleaver86, or the priori probability information D77 for an information bitwhich is of a value “0”, as selected by the changeover switch 87, andperforms soft output decoding, based on the channel response R_(ch) fromthe pre-stage of the precoder 54 in the recording system up to an outputin the equalizer 58, represented by the following equation (13):R _(ch)=(1−D)/(1⊕D)  (16)where ⊕ denotes exclusive OR, in accordance with the aforementioned BCJRalgorithm or SOVA. If the interleaved data D54 prior to the precoding bythe precoder 54 is represented as C(t), with 0≦t≦N, the channel SISOdecoder 81 computes the log posterior probability ratio log(P(C(t)=1)/P(C(t)=0)), as the posterior probability information forC(t), to route this log posterior probability ratio as the channeldecoded signal D71 to the downstream side difference taking unit 82.

The channel SISO decoder 81 is not limited to the aforementioneddecoders 20, 30, it being only sufficient if the channel SISO decoder 81is constructed as an SISO decoder. For example, it is sufficient if thechannel SISO decoder 81 performs soft output decoding, in accordancewith the aforementioned BCJR algorithm or SOVA, based on the trelliscorresponding to the channel response.

The difference taking unit 82 takes the difference between the channeldecoded signal D71, as a soft input, supplied from the channel SISOdecoder 81, and the priori probability information D76, as a soft input,supplied from the interleaver 86, to output data represented by thedifference value as a soft output to the post-stage deinterleaver 83, asthe channel extrinsic information signals D72 as the extrinsicinformation to an information bit as found by the code constraintcondition. Meanwhile, this channel extrinsic information signals D72corresponds to the interleaved data D54 as interleaved by theinterleaver 53 of the recording system.

The deinterleaver 83, as deinterleaving means, deinterleaves the channelextrinsic information signals D72, as a soft input, supplied from thedifference taking unit 82, in order to restore the bit sequence of theinterleaved data D54 from the interleaver 53 of the recording system tothe bit sequence of the original modulation encoded data D53. Thedeinterleaver 83 sends the deinterleaved data to the modulation SISOdecoder 84 and to the difference taking unit 85 as the deinterleavedsignal D73 which is the priori probability information to the code bitin the modulation SISO decoder 84.

The modulation SISO decoder 84 as modulation decoding means isconstructed as the aforementioned decoders 20, 30 and is an SISOdecoder. It is assumed that the modulation encoding is applied by themodulation coder 52 of the recording system with the code rate R=K/N,with the modulation encoded data D53 following modulation encoding bythe modulation coder 52 being M(t) (0≦t<N) and with the error correctioncoded data D52 prior to modulation encoding by the modulation coder 52being E(t) (0≦t<K). The modulation SISO decoder 84, fed as an input withthe deinterleaved signal D73 from the deinterleaver 83, calculates thelog posterior probability ratio log (P(M(t)=1)/P(M(t)=0)), as theposterior probability information for M(t), with the deinterleavedsignal D73 as an input from the channel, and sends the log posteriorprobability ratio as the modulation channel decoded signal D74 to thedifference taking unit 85. The modulation SISO decoder 84 alsocalculates the log posterior probability ratio log(P(E(t)=1)/P(E(t)=0)), as the posterior probability information forE(t), to route the log posterior probability ratio as the turbo decodedsignal D65 to the error correcting soft decoder 64.

The difference taking unit 85 finds a difference value between themodulation channel decoded signal D74, as a soft input, supplied fromthe modulation SISO decoder 84, and the deinterleaved signal D73 as asoft input from the deinterleaver 83, and outputs data given as thisdifference value to the post-stage interleaver 86 as a soft output asthe modulated extrinsic information signals D75 as the extrinsicinformation to the code bit as found by the constraint condition.

The interleaver 86, as the second interleaving means, interleaves themodulated extrinsic information signals D75, as a soft input fed fromthe difference taking unit 85, based on the same interleaving positioninformation as that of the interleaver 53 of the recording system. Theinterleaver 86 sends the interleaved data to the channel SISO decoder 81and to the difference taking unit 82 as being the priori probabilityinformation signal D76 for the information bit in the channel SISOdecoder 81.

In the initial stage of the decoding, the changeover switch 87 is set tothe fixed terminal a supplying a value 0 corresponding to the prioriprobability information signal D77 to select the priori probabilityinformation signal D77 as being the priori probability informationsignal D78 for an information bit in the channel SISO decoder 81. Thechangeover switch 87 then is set to a fixed terminal b supplying thepriori probability information signal D76 supplied from the interleaver86 to select the priori probability information signal D76 as being thepriori probability information signal D78.

The channel and modulation turbo decoder 63, is provided with themodulation SISO decoder 84 and the channel SISO decoder 81, ascounterparts to the modulation coder 52 and the precoder 54 of therecording system, respectively, as described above, to decompose thecode of high decoding complexity into elements with lower decodingcomplexity, such as to sequentially improve characteristics by theinteraction between the channel SISO decoder 81 and the modulation SISOdecoder 84. If fed with the digital channel signal D62, as a soft input,from the A/D converter 60, the channel and modulation turbo decoder 63iterates the decoding operations from the channel SISO decoder 81 to themodulation SISO decoder 84 a pre-set number of times, such as several totens of times, to route the soft-output log posterior probability ratio,obtained on decoding a pre-set number of times, as the turbo decodedsignal D65 to the post-stage error correcting soft decoder 64.

In reproducing data recorded on the recording medium 70, the reproducingsystem of the magnetic recording and/or reproducing apparatus 50turbo-decodes the soft-input digital channel signal D62, generatedthrough the readout head 57, equalizer 58, gain adjustment circuit 59and the A/D converter 60, by the channel and modulation turbo decoder63, to generate the turbo decoded signal D65 corresponding to the errorcorrection coded data D52 input to the modulation coder 52 in therecording system.

This reproducing system soft-decodes the turbo decoded signal D65,generated by the channel and modulation turbo decoder 63, for errorcorrection codes, by the error correcting soft decoder 64, to outputdata as resulting soft output directly to outside as output data D66, orbinary-codes the soft-output data to generate hard-output data D66,which is issued to outside.

The reproducing system of the magnetic recording and/or reproducingapparatus 50 is provided in this manner with the channel and modulationturbo decoder 63 and performs turbo decoding between the modulation SISOdecoder 84 and the channel SISO decoder 81 corresponding to themodulation coder 52 and the precoder 54 of the recording system torealize decoding in meeting with the channel response and the modulationencoding.

In the above-described magnetic recording and/or reproducing apparatus50, in which the interleaver 53 is provided in the recording system onthe post-stage of the modulation coder 52 to execute encoding by serialconcatenated code between the modulation coder 52 and the precoder 54,while it is provided on the reproducing system with the channel andmodulation turbo decoder 63 to effect turbo decoding to realize highperformance coding. In addition, turbo decoding with high efficiency canbe realized by exploiting soft information for the entire decodingprocessing for the code, thus eliminating the necessity of diminishingthe information. The result is the appreciably lowered decoding errorrate.

The second embodiment of the magnetic recording and/or reproducingapparatus is now explained. The magnetic recording and/or reproducingapparatus executes encoding as correlation is afforded to fore and aftside data instead of coding/decoding on the block basis. In addition,the magnetic recording and/or reproducing apparatus performs trellisdecoding conforming to the constraint condition.

An interleaver used for the recording system of the magnetic recordingand/or reproducing apparatus is first explained.

An interleaver applied to the recording system, such a one may be usedwhich is configured similarly to the interleaver 10 shown in FIG. 5 andin which data is interleaved based on the modulation encoding block ofthe trellis to re-array the data bit sequence. It is assumed here thatthe bit sequence of the data from the modulation encoding of generatingthree output bits for two input bits in accordance with the conversiontable shown in Table 3 by an interleaver. If the constraint condition tobe met by the modulation encoded data is (d, k)=(0, 2) limitation, theinterleaver generates a sequence meeting the (d, k)=(0, 4) limitation.

The interleaver is not limited to one interleaving the data based on themodulation encoding block of the trellis, such that any suitableinterleaver interleaving the data such as to meet the pre-set constraintcondition following interleaving may be used.

Referring to FIGS. 11 to 14, the encoder used in the recording systemand the SISO decoder used for the reproducing system of the magneticrecording and/or reproducing apparatus is explained. It is noted that,although the coder and the decoder, used for modulation encoding andmodulation decoding, respectively, are shown here, the coder and thedecoder for the channel are configured in a similar fashion.

The magnetic recording and/or reproducing apparatus performs modulationencoding and modulation decoding, based on a common trellis. Althoughthe trellis structure is changed depending on limitations imposed on themodulation code, the modulation encoding and modulation decoding,satisfying the (d, k)=(0, 2) limitations, with the code rate R=2/3, ishere explained.

FIG. 11 shows a diagram showing the status transition for generatingsatisfying the (d, k)=(0, 2) limitations. In FIG. 11, labels affixedbetween the respective states indicate bits output in case of statustransition. For example, if the status transition that has occurred is“S0→S1→S2”, an output bit string is “00”. The bit string output in casestatus transition has occurred in accordance with the aforementionedstatus transition diagram necessarily satisfies the (d, k)=(0, 2)limitations.

Assume that the modulation encoding of outputting a 3 bit modulated codefor a 2-bit input, with the code rate R=2/3. For generating themodulation code satisfying the (d, k)=(0, 2) limitations, it isapparently sufficient if status transition occurs thrice in accordancewith the status transition diagram shown in FIG. 11, with the resultingoutput being a modulated code.

The trellis when the status transition has occurred thrice in accordancewith the status transition diagram shown in FIG. 11, that is, a diagramobtained on developing the status transition diagram along the time axisdirection, is as shown in FIG. 12. For example, in the trellis shown inFIG. 12, a branch lying at an uppermost position indicates that there isone path starting at the status S2 and again getting to the status S2after three status transitions, with a corresponding output being “100”.

In case of modulation encoding of outputting 3-bit modulated code for a2-bit input, 2²=4 branches are selected from each state, these branchesbeing then allocated to 2-bit inputs of “00, 01, 10, 11” to form atrellis in which an input is associated with an output. FIG. 13 shows atrellis formed on branch selection as described above. In FIG. 13, eachlabel affixed between different states indicate an input/output. Forexample, in the trellis shown in FIG. 13, a branch S0→S2 indicates that,if “11” is input for the state S0, status transition occurs to thestatus S2, as “100” is output.

The encoder, applied to the magnetic recording and/or reproducingapparatus, shown as the second embodiment, repeats the status transitionfor encoding, in accordance with the trellis formed by theabove-described sequence of operations, to generate a modulated codestring having correlation between input data. The encoder may beprovided with components shown for example in FIG. 14.

The encoder 90, shown in FIG. 14, includes a state register 91 forholding the state of the encoder 90, a next-state calculating circuit92, for calculating the next transition state, and an output signalcalculating circuit 93 for calculating an output signal D94.

The state register 91 is a 2-bit register holding 2 bits specifying thestate of the current encoder 90. The state register 91 sends a statussignal D92, specifying the 2 bits indicating the current state, to thenext-state calculating circuit 92 and to the output signal calculatingcircuit 93, as the state register 91 holds 2 bits indicating the nextstate corresponding to the next state signal D93 supplied from thenext-state calculating circuit 92.

When fed with the input signal D91 and with the status signal D92,supplied from the state register 91, the next-state calculating circuit92 calculates the next state in accordance with the followinginput/output correlating table 4:

TABLE 4 Typical Input/Output Correlating Table status signals inputsignals next-state signals 0 00 0 0 01 1 0 10 1 0 11 2 1 00 1 1 01 0 110 0 1 11 2 2 00 2 2 01 0 2 10 0 2 11 1 3 00 0 3 01 0 3 10 0 3 11 0

The next-state calculating circuit 92 sends the next state signal D93 tothe state register 91.

If fed with the input signal D91 and with the status signal D92,supplied from the state register 91, the output signal calculatingcircuit 93 calculates an output signal D94, in accordance with thefollowing input/output correlating table 5:

TABLE 5 Typical Input/Output Correlating Table status signals inputsignals output signals 0 00 111 0 01 110 0 10 010 0 11 100 1 00 110 1 01011 1 10 111 1 11 100 2 00 100 2 01 101 2 10 111 2 11 110 3 00 111 3 01111 3 10 111 3 11 111

Meanwhile, this output signal D94 satisfies the (d, k)=(0, 2)limitations.

When fed with the input signal D91, the encoder 90 calculates the nextstate, using this input signal D91 and the status signal D92, by thenext-state calculating circuit 92, for storage sequentially in the stateregister 91. The encoder 90 calculates an output signal D94, by theoutput signal calculating circuit 93, using the input signal D91 and thestatus signal D92, by the output signal calculating circuit 93, tooutput the so-calculated output signal D94.

Since there lacks the status S3 in the encoder 90, if transition to thestatus S3 occurs before the resetting of the encoder 90, an outputsignal “111” is instantly output as an output signal D94, based on theTable 5, to realize the function of resetting to the state S0.

A decoder for modulation decoding the signal, encoded by theabove-described encoder, applies the decoding, which is based on theBCJR or SOVA algorithm, in accordance with the trellis previouslyexplained with reference to FIG. 13. With this decoder, the magneticrecording and/or reproducing apparatus is able to perform trellisdecoding exploiting the signal correlation in the modulation encoder.

In particular, if, in performing trellis decoding in the magneticrecording and/or reproducing apparatus, SISO decoding of the BCJR orSOVA algorithm is used in the decoder, the soft information can beoutput to the error correction decoding circuit provided downstream ofthe modulation decoder, thereby improving the decoding error rate.

The magnetic recording and/or reproducing apparatus, employing this typeof the encoder and the decoder, is hereinafter explained with referenceto FIG. 15.

The magnetic recording and/or reproducing apparatus 100, shown in FIG.15, includes, as a recording system for recording data on a recordingmedium 70, an error correction encoder 101 for error correction encodinginput data, a modulation encoder 101, a modulation encoder 102 formodulation encoding input data, an interleaver 103 for re-arraying theinput data in its sequence, a precoder 104 for filtering input data forcompensating its channel characteristics, a write current driver 105 forconverting respective bits of the input data into write current values,and a write head 106 for recording data on the recording medium 70.

Similarly to the error correction coder 51 in the magnetic recordingand/or reproducing apparatus 50, the error correction encoder 101, aserror correcting encoding means, error correction encodes the input dataD101. The error correction encoder 101 sends the error correctionencoded data D102 to the downstream side modulation encoder 102.

The modulation encoder 102, as modulation encoding means, is configuredas the aforementioned modulation encoder 90. Specifically, it is amodulation encoder for repeating status transitions in accordance withthe trellis, by way of encoding, for generating a modulated code stringexhibiting correlation between input data. The modulation encoder 102applies pre-set trellis modulation coding to the error correction codeddata D102, supplied from the error correction encoder 101, to generatemodulated encoded data D103 as a string subjected to limitation. Themodulation encoder 102 sends the generated modulation encoded data D103to the downstream side interleaver 103.

The interleaver 103, as (first) interleaving means, interleaves themodulated encoded data D103 in terms of the trellis modulation encodingblock as a unit, to re-array the sequence of bits making up themodulated encoded data D103. The interleaver 103 sends the generatedinterleaved data D104 to the downstream side precoder 104.

Similarly to the precoder 54 of the aforementioned magnetic recordingand/or reproducing apparatus 50, the precoder 104 filters theinterleaved data D104, supplied from the interleaver 103, in such amanner as to compensate for channel characteristics from the datawriting to the recording medium 70 to the output in the equalizer 108 inthe reproducing system, thereby generating a precode signal D105 as abinary signal. The precoder 104 sends the so-generated precede signalD105 to the downstream side write current driver 105.

Similarly to the write current driver 55 in the aforementioned magneticrecording and/or reproducing apparatus 50, the write current driver 105converts respective bits of the precode signal D104, supplied from theprecoder 103, into the write current value I_(S), to generate a writecurrent signal D106. The write current driver 105 sends the generatedwrite current signal D106 to a downstream side write head 106.

Similarly to the write head 56 in the aforementioned magnetic recordingand/or reproducing apparatus 50, the write head 106 applies a magneticwrite signal D107, corresponding to the write current signal D106supplied from the write current driver 105, to the recording medium 70,to record data thereon.

In recording data on the recording medium 70, the recording system inthe magnetic recording and/or reproducing apparatus 100 error correctionencodes the input data D101 by the error correction encoder 101. Therecording system then applies pre-set trellis modulation encoding toerror correction encoded data D102 by the modulation encoder 102 andinterleaves the modulated encoded data D103 by the interleaver 103 basedon the pre-set trellis modulation encoding block to generate a precedesignal D105 by the precoder 104.

The recording system records the precode signal D105, generated by theprecoder 104, on the recording medium 70, by the write current driver105 and the write head 106.

The recording system of the magnetic recording and/or reproducingapparatus 100, thus having the interleaver 103 downstream of themodulation encoder 102, effects encoding by serial concatenated codingbetween the modulation encoder 102 and the precoder 104 to realize highperformance coding as modulation encoding and channel coding downstreamof the error correction coding.

As the reproducing system for reproducing data recorded on the recordingmedium 70, the magnetic recording and/or reproducing apparatus 100includes a readout head 107 for reading out data recorded on therecording medium 70, an equalizer 108 for equalizing input data, a gainadjustment circuit 109 for adjusting the gain of the input data, an A/Dcircuit 110 for converting analog data to digital data, a timing circuit111 for reproducing clocks, a gain adjustment control circuit 112 forcontrolling the gain adjustment circuit 109, a modulation turbo decoder113 for turbo-decoding the input data and an error correction softdecoder 104 for error correction soft decoding the input data.

Similarly to the readout head 57 of the magnetic recording and/orreproducing apparatus 50, a readout head 107 reads out the readoutmagnetization signal D108 from the recording medium 70 to generate areadout current signal D109 conforming to the readout magnetizationsignal D108. The readout head 107 sends the so-generated current signalD109 to the downstream side equalizer 108.

Similarly to the equalizer 58 of the magnetic recording and/orreproducing apparatus 50, the equalizer 108 equalizes the readoutcurrent signal D109, supplied from the readout head 107, so that thechannel response from the data writing on the recording medium 70 in therecording system up to the outputting at the equalizer 108 will be ofpre-set characteristics, to generate an equalized signal D110. Theequalizer 108 routes the generated equalized signal D110 to thedownstream side gain adjustment circuit 109.

Similarly to the gain adjustment circuit 59 Of the magnetic recordingand/or reproducing apparatus 50, the gain adjustment circuit 109 adjuststhe gain of the equalized signal D110 supplied from the equalizer 108,based on a gain adjustment control signal D114, supplied from the gainadjustment control circuit 112, to generate a gain adjustment signalD111. The gain adjustment circuit 109 routes the generated gainadjustment signal D111 to the downstream side A/D converter 110.

Similarly to the A/D converter 60 of the magnetic recording and/orreproducing apparatus 50, the A/D converter 110 samples and digitizesthe gain adjustment signal D111, supplied from the gain adjustmentcircuit 109, based on the clock signal D113, supplied from the timingregenerating circuit 111, to generate a digital channel signal D112. TheA/D converter 110 sends the generated digital channel signal D112 to thetiming regenerating circuit 111, gain adjustment control circuit 112 andto the channel and modulation turbo decoder 113.

Similarly to the timing generating circuit 61 of the magnetic recordingand/or reproducing apparatus 50, the timing regenerating circuit 111regenerates clocks from the digital channel signal D112 supplied fromthe A/ID converter 110 to generate clock signals D113. The timingregenerating circuit 111 sends the generated clock signals D113 to theA/D converter 110.

Similarly to the gain adjustment control circuit 62 of the magneticrecording and/or reproducing apparatus 50, the gain adjustment controlcircuit 112 generates, based on the digital channel signal D112,supplied from the A/D converter 110, a gain adjustment control signalD114, which is a control signal used for maintaining the amplitude ofthe equalized signal D110 at an expected value. The gain adjustmentcontrol circuit 112 sends the generated gain adjustment control signalD114 to the gain adjustment circuit 109.

Similarly to the channel and modulation turbo decoder 63 of the magneticrecording and/or reproducing apparatus 50, the channel and modulationturbo decoder 113, is comprised of concatenated SISO decoders to effectturbo decoding. The channel and modulation turbo decoder 113turbo-decodes the input digital channel signal D112 from the A/Dconverter 110 to route the generated turbo decoded signal D115 to thedownstream side error correction decoder 114.

Similarly to the error correction soft decoder 54 of the magneticrecording and/or reproducing apparatus 50, the error correction softdecoder 114, as error correcting soft decoding means, soft-decoded theturbo decoded signal D115 supplied from the modulation SISO decoder 113for errors based on the BCJR algorithm or SOVA to output soft or hardoutput data D116 to outside.

Referring to FIG. 16, the channel and modulation turbo decoder 113 isexplained in detail.

In this figure, the channel and modulation turbo decoder 113 includes achannel SISO decoder 121, as an SISO decoder for decoding the channelresponse from the pre-stage of the precoder 104 in the recording systemto the outputting in the equalizer 108, a deinterleaver 123 forrestoring the sequence of the input data, an SISO decoder 124, as a SISOdecoder for modulation decoding the input data, an interleaver 126 forre-arraying the sequence of the input data, a changeover switch 127 forchanging over input data input as the priori probability information forinformation bits and two difference taking units 122, 125.

The channel SISO decoder 121, as channel decoding means, is fed with thedigital channel signal D112, as a soft input supplied from the A/Dconverter 110, and with priori probability information D128, as selectedby the changeover switch 127 from the priori probability informationD126 for information bits supplied as soft input from the A/D converter110 and the priori probability information D127 for information bitshaving a value of “0”, to effect soft output decoding, based on the BCJRalgorithm or SOVA, in accordance with the trellis for the channelresponse from the parentage of the precoder 104 in the recording systemto an output in the equalizer 108 in the reproducing system. If theinterleaved data D104 prior to precoding by the precoder 104 isexpressed as C(t) (0≦t≦N), the channel SISO decoder 121 calculates thelog posterior probability ratio log (P(C(t)=1)/P(C(t)=0)), as theposterior probability information for this C(t), to send this logposterior probability ratio as the channel decoded signal D121 to thedownstream side difference taking unit 122.

The difference taking unit 122 finds a difference between the channeldecoded signal D121, as soft input, supplied from the channel SISOdecoder 121, and the priori probability information D126, as soft input,supplied from the interleaver 126, to output data corresponding to thisdifference value as soft output to the downstream side deinterleaver 123as the channel extrinsic information signals D122 for an information bitas found by the code constraint condition. Meanwhile, the channelextrinsic information signals D122 corresponds to the interleaved dataD104 obtained on interleaving by the interleaver 103 in the recordingsystem.

The deinterleaver 123, as deinterleaving means, deinterleaves the bitsequence of the interleaved data D104 from the interleaver 103 of therecording system to the channel extrinsic information signals D122supplied from the difference taking unit 122 in order to restore the bitsequence to that of the original modulated encoded data D103. Thedeinterleaver 123 sends the deinterleaved data to the modulation SISOdecoder 124 and to the difference taking unit 122 as the deinterleavedsignal D123 which is the priori probability information for the codebits in the modulation SISO decoder 124.

The modulation SISO decoder 124, as modulation decoding means, decodessignals encoded by the modulation encoder 102 in the recording system,and is an SISO type modulation decoder. The modulation encoded dataD103, obtained on modulation encoding by the modulation encoder 102 witha code rate R=K/N, is specified as M(t) (0≦t<N) and the error correctionencoded data D102 prior to modulation encoding by the modulation encoder102 is specified as E(t) (0≦t<K). The modulation SISO decoder 124 is fedwith the deinterleaved signal D123, supplied as soft input from thedeinterleaver 123, and calculates the log posterior probability ratiolog (P(M(t)=1)/P(M(t)=0)), as posterior probability information forM(t), using the trellis corresponding to the constraint condition, tosend the so-calculated log posterior probability ratio as the modulationchannel decoded signal D124 to the difference taking unit 125. Themodulation SISO decoder 124 also calculates the log posteriorprobability ratio log (P(E(t)=1)/P(E(t)=0)), as posterior probabilityinformation for E(t), to send the so-calculated log posteriorprobability ratio as the turbo decoded signal D115 to the errorcorrection soft decoder 114.

The difference taking unit 125 finds a difference between the modulationchannel decoded signal D124, supplied as soft input from the modulationSISO decoder 124, and the deinterleaved signal D123, supplied as softinput from the deinterleaver 123, to output the data as the differencevalue as soft output to the downstream side interleaver 126 as themodulated extrinsic information signals D125, which is the extrinsicinformation for a code bit as found by the code constraint condition.

The interleaver 126, as second interleaving means, interleaves themodulated extrinsic information signals D125, supplied from thedifference taking unit 125, based on the same interleaving positioninformation as that of the interleaver 103 of the recording system. Theinterleaver 126 sends the interleaved data to the channel SISO decoder121 and to the difference taking unit 122 as being the prioriprobability information signal D126 for the information bit in thechannel SISO decoder 121.

In the initial stage of the decoding, the changeover switch 127 is setto the fixed terminal c supplying a value 0 corresponding to the prioriprobability information signal D127 to select the priori probabilityinformation signal D127 as being the priori probability informationsignal D128 for an information bit in the channel SISO decoder 121. Thechangeover switch 127 then is set to a fixed terminal d supplying thepriori probability information signal D126 supplied from the interleaver126 to select the priori probability information signal D126 as beingthe priori probability information signal D128.

Similarly to the channel and modulation turbo decoder 63 in thepreviously described magnetic recording and/or reproducing apparatus,the channel and modulation turbo decoder 113, is provided with themodulation SISO decoder 124 and the channel SISO decoder 121, ascounterparts to the modulation coder 102 and the precoder 104 of therecording system, respectively, as described above, to decompose thecode of high decoding complexity into elements with lower decodingcomplexity, such as to sequentially improve characteristics by theinteraction between the channel SISO decoder 121 and the modulation SISOdecoder 124. If fed with the digital channel signal D112, as a softinput, from the A/D converter 110, the channel and modulation turbodecoder 113 iterates the decoding operations from the channel SISOdecoder 121 to the modulation SISO decoder 124 a pre-set number oftimes, such as several to tens of times, to route the soft-output logposterior probability ratio, obtained on decoding a pre-set number oftimes, as the turbo decoded signal D115 to the post-stage errorcorrecting soft decoder 64.

In reproducing data recorded on the recording medium 70, the reproducingsystem of the magnetic recording and/or reproducing apparatus 50turbo-decodes the soft-input digital channel signal D112, generatedthrough the readout head 107, equalizer 108, gain adjustment circuit 109and the A/D converter 110, by the channel and modulation turbo decoder113, to generate the turbo decoded signal D115 corresponding to theerror correction coded data D102 input to the modulation coder 102 inthe recording system.

This reproducing system soft-decodes error correction codes of the turbodecoded signal D115, generated by the channel and modulation turbodecoder 113, by the error correcting soft decoder 114, to output data asresulting soft output directly to outside as output data D116, orbinary-codes the soft-output data to generate hard-output data D116which is issued to outside.

The reproducing system of the magnetic recording and/or reproducingapparatus 100 is provided in this manner with the channel and modulationturbo decoder 113 and performs turbo decoding between the modulationSISO decoder 124 and the channel SISO decoder 121 corresponding to themodulation coder 102 and the precoder 104 of the recording system torealize decoding in meeting with the channel response and the modulationencoding.

The magnetic recording and/or reproducing apparatus 100 includes, in itsrecording system, the interleaver 103 downstream oft the modulationencoder 102, to effect encoding by serial concatenated code between themodulation encoder 102 and the precoder 104, while including, on itsreproducing side, the channel and modulation turbo decoder 113 to effectturbo decoding to realize high performance coding as well as highlyefficient turbo decoding exploiting the soft information for the entiredecoding processing for the code. Since there is no necessity ofdiminishing the information, the decoding error rate can be loweredsignificantly. Moreover, the magnetic recording and/or reproducingapparatus 100 effects coding in the recording system, as correlation isafforded to the fore and aft side data. In addition, trellis decodingcan be performed on the reproducing side in meeting with the constraintcondition, thus further lowering the decoding error rate.

The above-described magnetic recording and/or reproducing apparatus 50,100 are able to perform efficient turbo decoding by exploiting the softinformation, thereby lowering the decoding error rate. In particular,with the magnetic recording and/or reproducing apparatus 100, encodingcan be made as correlation is afforded to the fore and aft side data,without doing block-based encoding or decoding, while trellis decodingcan be made in meeting with the constraint conditions, thus furtherlowering the decoding error rate. That is, the magnetic recording and/orreproducing apparatus 50, 100 is able to realize high precisiondecoding, thus assuring high operational reliability fort the user.

The present invention is not limited to the above-described embodiment.For example, the present invention may be applied to a recording medium70 other than the recording medium of the magnetic recording system,that is to a recording medium by the optical recording system, such as aso-called CD (Compact Disc) or to the DVD (Digital Versatile Disc) or toa recording medium of the photomagnetic recording system, such as aso-called magneto-optical disc (MO) disc.

In the above-described embodiment, it is assumed that the magneticrecording and/or reproducing apparatus 100 performs trellis modulationencoding on the encoder side and trellis modulation decoding on thedecoder side. However, the present invention is applicable to such acase wherein the trellis modulation decoding is performed on the decoderside to output a soft decision value even in case the trellis modulationencoding is not performed on the encoding side, as when block modulationis effected on the encoder side.

Moreover, in the above-described embodiment, it is assumed that themagnetic recording and/or reproducing apparatus 50 or 100 is a unitaryapparatus provided with the recording and reproducing systems.Alternatively, a unitary recording apparatus may be configured as arecording system for recording data on a recording medium, while aunitary reproducing apparatus may also be configured as a reproducingsystem for reproducing the data recorded on the recording apparatus.

In the foregoing, the present invention has been disclosed only by wayof illustration and should not be interpreted in a limiting fashion. Thescope of the present invention is to be interpreted in light of thedescription of the following claims.

1. A data reproducing apparatus for reproducing data recorded by arecording equipment for recording data on a recording medium, therecording equipment including modulation encoding means for applyingpredetermined modulation encoding to input data, the input data having abit sequence, wherein said modulation encoding means encodes the inputdata in accordance with a constraint condition by block modulation, andfirst interleaving means for interleaving data supplied from saidmodulation encoding means for re-arraying a data sequence correspondingto said data supplied from said modulation encoding means, said datareproduction apparatus comprising: deinterleaving means fordeinterleaving reproduced data in a sequence such as to restore the datasequence to the bit sequence; modulation decoding means for modulationdecoding data supplied from said deinterleaving means in conformancewith said constraint condition, wherein said modulation decoding meansincludes likelihood calculating means for calculating a likelihood valuecorresponding to output codewords output by said modulation encodingmeans, wherein posterior probability information as a soft decisionvalue for an input bit to said modulation encoding means and an outputbit from said modulation encoding means is calculated using saidlikelihood value as calculated by said likelihood calculating means; andsecond interleaving means for interleaving difference data correspondingto a difference between data output by said modulation decoding meansand data output by said deinterleaving means, based on the sameinterleaving position information as that of said first interleavingmeans, for re-arraying the sequence of the difference data.
 2. The datareproducing apparatus according to claim 1, wherein said modulationdecoding means is fed with a soft input signal and outputs a soft outputsignal.
 3. The data reproducing apparatus according to claim 1, whereinsaid recording equipment includes precode means for filtering datasupplied from said first interleaving means to compensate for channelcharacteristics, and the data reproducing apparatus further comprising:channel decoding means for decoding a channel response.
 4. The datareproducing apparatus according to claim 3, wherein said channeldecoding means is fed with a soft input signal and performs soft outputdecoding.
 5. The data reproducing apparatus according to claim 3,wherein said channel decoding means is fed with a soft input signal andperforms soft output decoding based on a trellis corresponding to thechannel response.
 6. The data reproducing apparatus according to claim4, wherein said deinterleaving means interleaves data corresponding to adifference between data output by said channel decoding means and dataoutput from said second interleaving means; and wherein said modulationdecoding is iteratively performed between said modulation decoding meansand said channel decoding means.
 7. The data reproducing apparatusaccording to claim 6, wherein said recording equipment includes errorcorrection encoding means for error correction encoding input data tosupply data resulting from the error correction encoding to saidmodulation encoding means, and the data reproducing apparatus furthercomprises: error correcting soft decoding means for soft decoding anerror correction code of the soft input signal corresponding to softoutput data obtained by said modulation decoding means as a result ofiterative decoding.
 8. The data reproducing apparatus according to claim1, wherein said first interleaving means interleaves data encoded bysaid modulation encoding means.
 9. The data reproducing apparatusaccording to claim 1, wherein said modulation decoding means effectsperforms decoding based on a trellis corresponding to said constraintcondition.
 10. The data reproducing apparatus according to claim 1,wherein said first interleaving means interleaves data encoded withblock modulation by said modulation encoding means in terms of amodulation encoding block as a unit.
 11. The data reproducing apparatusaccording to claim 1, wherein said modulation encoding means encodesinput data in accordance with said trellis conforming to said constraintcondition; and said modulation decoding means performs decoding based ona trellis conforming to said constraint condition.
 12. The datareproducing apparatus according to claim 11, wherein said firstinterleaving means interleaves data encoded by said modulation encodingmeans in terms of a modulation encoding block of said trellis as a unit.13. The data reproducing apparatus according to claim 2, wherein saidmodulation decoding means performs soft output decoding based on theBCJR algorithm or on the SOVA algorithm.
 14. The data reproducingapparatus according to claim 1, data is recorded on said recordingmedium by a magnetic, optical or magneto-optical system.
 15. A datareproducing method for reproducing data recorded by a recording methodfor recording data on a recording medium including a modulation encodingstep of applying predetermined modulation encoding to input data havinga bit sequence, encoding the input data in accordance with a constraintcondition using block modulation, and a first interleaving step ofinterleaving data encoded in said modulation encoding step, forre-arraying a data sequence corresponding to said data encoded in saidmodulation encoding step, said data reproduction method comprising thesteps of: deinterleaving the input data in a sequence such as to restorethe data sequence to the bit sequence; modulation decoding data suppliedfrom said step of deinterleaving, in conformance with said constraintcondition, wherein the step of modulation decoding further includes alikelihood calculating step of calculating a likelihood value of outputcodewords generated and output by said modulation encoding step;calculating posterior probability information as a soft decision valuefor an input bit to said modulation encoding step and an output bit fromsaid modulation encoding step using said likelihood value as calculatedby said likelihood calculating step; and interleaving difference datacorresponding to a difference between data decoded in said modulationencoding step and data re-arrayed in said step of deinterleaving, basedon the same interleaving position information as that of said firstinterleaving step, for re-arraying the sequence of the difference data.16. The data reproducing method according to claim 15, wherein said stepof modulation decoding is fed with a soft input signal and outputs asoft output signal.
 17. The data reproducing method according to claim15, wherein said recording method includes a precode step of filteringdata supplied from said first interleaving step to compensate forchannel characteristics, and the data reproducing method furthercomprising: channel decoding a channel response.
 18. The datareproducing method according to claim 17, wherein said step of channeldecoding is fed with a soft input signal and performs soft outputdecoding.
 19. The data reproducing method according to claim 17, whereinsaid step of channel decoding is fed with a soft input signal andperforms soft output decoding based on a trellis corresponding to thechannel response.
 20. The data reproducing method according to claim 18,wherein said step of deinterleaving interleaves data corresponding to adifference between data decoded in said step of channel decoding anddata re-arrayed in said step of interleaving; iteratively performingdecoding between said step of modulation decoding and said step ofchannel decoding.
 21. The data reproducing method according to claim 20,wherein said recording method includes an error correction encoding stepof error correction encoding input data to supply data resulting fromthe error correction encoding to said modulation encoding step, and thedata reproducing method further comprising: soft decoding an errorcorrection code of the soft input signal corresponding to soft outputdata obtained by said modulation decoding step as a result of iterativedecoding.
 22. The data reproducing method according to claim 15, whereinsaid first interleaving step interleaves data encoded by said modulationencoding step so that the constraint condition is satisfied.
 23. Thedata reproducing method according to claim 15, wherein said modulationdecoding step effects performs decoding based on a trellis correspondingto said constraint condition.
 24. The data reproducing method accordingto claim 15, wherein said first interleaving step interleaves dataencoded with block modulation by said modulation encoding step in termsof a modulation encoding block as a unit.
 25. The data reproducingmethod according to claim 15, wherein said modulation encoding stepencodes input data in accordance with the trellis conforming to saidconstraint condition; and said step of modulation decoding performsdecoding based on a trellis conforming to said constraint condition. 26.The data reproducing method according to claim 25, wherein said firstinterleaving step interleaves data encoded by said modulation encodingstep in terms of a modulation encoding block of said trellis as a unit.27. The data reproducing method according to claim 16, wherein said stepof modulation decoding performs soft output decoding based on the BCJRalgorithm or on the SOVA algorithm.
 28. The data reproducing methodaccording to claim 15, wherein data is recorded on said recording mediumby a magnetic, optical or magneto-optical system.
 29. A data recordingand reproducing apparatus for recording and reproducing data for arecording medium, said apparatus comprising: modulation encoding meansfor applying predetermined modulation encoding to input data having abit sequence, wherein said modulation encoding means encodes the inputdata in accordance with a constraint condition by block modulation;first interleaving means for interleaving data supplied from saidmodulation encoding means for re-arraying a data sequence correspondingto said data supplied from said modulation encoding means;deinterleaving means for deinterleaving reproduced data in a sequencesuch as to restore the data sequence to the bit sequence; modulationdecoding means for modulation decoding data supplied from saiddeinterleaving means in conformance with said constraint condition,wherein said modulation decoding means further includes: likelihoodcalculating means for calculating a likelihood value corresponding tooutput codewords output by said modulation encoding means, whereinposterior probability information as a soft decision value for an inputbit to said modulation encoding means and an output bit from saidmodulation encoding means is calculated using said likelihood value ascalculated by said likelihood calculating means; and second interleavingmeans for interleaving difference data corresponding to a differencebetween data output by said modulation decoding means and data output bysaid deinterleaving means, based on the same interleaving positioninformation as that of said first interleaving means, for re-arrayingthe sequence of the difference data.
 30. The data recording andreproducing apparatus according to claim 29, wherein said modulationdecoding means is fed with a soft input signal and outputs a soft outputsignal.
 31. The data recording and reproducing apparatus according toclaim 29, further comprising: precode means for filtering data suppliedfrom said first interleaving means to compensate for channelcharacteristics, and channel decoding means for decoding a channelresponse.
 32. The data recording and reproducing apparatus according toclaim 31, wherein said channel decoding means is fed with a soft inputsignal and performs soft output decoding.
 33. The data recording andreproducing apparatus according to claim 31, wherein said channeldecoding means is fed with a soft input signal and performs soft outputdecoding based on a trellis corresponding to the channel response. 34.The data recording and reproducing apparatus according to claim 32,wherein said deinterleaving means interleaves data corresponding todifference between the data output by said channel decoding means anddata output from said second interleaving means; and wherein saidmodulation decoding is iteratively performed between said modulationdecoding means and said channel decoding means.
 35. The data recordingand reproducing apparatus according to claim 34, further comprising:error correction encoding means for error correction encoding inputdata, wherein said modulation encoding means modulation encodes datasupplied from said error correction encoding means; and error correctingsoft decoding means for soft decoding an error correction code of thesoft input signal corresponding to the soft output data obtained by saidmodulation decoding means as a result of iterative decoding.
 36. Thedata recording and reproducing apparatus according to claim 29, whereinsaid first interleaving means interleaves data encoded by saidmodulation encoding means.
 37. The data recording and reproducingapparatus according to claim 29, wherein said modulation decoding meansperforms decoding based on a trellis corresponding to said constraintcondition.
 38. The data recording and reproducing apparatus according toclaim 29, wherein said first interleaving means interleaves data encodedwith block modulation by said modulation encoding means in terms of amodulation encoding block as a unit.
 39. The data recording andreproducing apparatus according to claim 29, wherein said modulationencoding means encodes input data in accordance with said trellisconforming to said constraint condition; and said modulation decodingmeans performs decoding based on a trellis conforming to said constraintcondition.
 40. The data recording and reproducing apparatus according toclaim 39, wherein said first interleaving means interleaves data encodedby said modulation encoding means in terms of a modulation encodingblock of said trellis as a unit.
 41. The data recording and reproducingapparatus according to claim 30, wherein said modulation decoding meansperforms soft output decoding based on the BCJR algorithm or on the SOVAalgorithm.
 42. The data recording and reproducing apparatus according toclaim 29, wherein data is recorded on said recording medium by amagnetic, optical or magneto-optical system.
 43. A data recording andreproducing method for recording and reproducing data for a recordingmedium, said method comprising the steps of: applying predeterminedmodulation encoding to input data having a bit sequence, wherein saidmodulation encoding encodes the input data in accordance with aconstraint condition by block modulation; interleaving themodulation-encoded data for re-arraying a data sequence corresponding tothe modulation-encoded data; deinterleaving reproduced data in asequence such as to restore the data sequence to the bit sequence;modulation decoding the data supplied from said step of deinterleavingin accordance with said constraint condition, wherein said step ofmodulation decoding further includes a likelihood calculating step forcalculating a likelihood value corresponding to each output codewordoutput by said modulation encoding step; calculating posteriorprobability information as a soft decision value for an input bit tosaid step of applying and an output bit from said step of applying usingsaid likelihood value as calculated by said likelihood calculating step;and interleaving difference data corresponding to a difference betweendata decoded in said step of modulation decoding and data re-arrayed insaid step of deinterleaving based on the same interleaving positioninformation as that of said step of interleaving the modulation-encodeddata.
 44. The data recording and reproducing method according to claim43, wherein said step of modulation decoding is fed with a soft inputsignal and outputs a soft output signal.
 45. The data recording andreproducing method according to claim 43, further comprising: filteringdata supplied from said step of interleaving the modulation-encoded datato compensate for channel characteristics, and channel decoding achannel response.
 46. The data recording and reproducing methodaccording to claim 45, wherein said step of channel decoding is fed witha soft input signal and performs soft output decoding.
 47. The datarecording and reproducing method according to claim 45, wherein saidstep of channel decoding is fed with a soft input signal and performssoft output decoding based on a trellis corresponding to the channelresponse.
 48. The data recording and reproducing method according toclaim 47, wherein said step of deinterleaving interleaves datacorresponding to data between data output by said step of channeldecoding and data output from said step of interleaving the differencedata; and iteratively performs decoding between said step of modulationdecoding and said step of channel decoding.
 49. The data recording andreproducing method according to claim 48, further comprising: errorcorrection encoding input data, wherein said step of applying modulationencodes data supplied from said step of error correction encoding; andsoft decoding a error correction code of the soft input signalcorresponding to soft output data obtained by said step of modulationdecoding as a result of iterative decoding.
 50. The data recording andreproducing method according to claim 43, wherein said step ofinterleaving the modulation-encoded data interleaves themodulation-encoded data so that the constraint condition is satisfied.51. The data recording and reproducing method according to claim 43,wherein said step of modulation decoding performs decoding based on atrellis corresponding to said constraint condition.
 52. The datarecording and reproducing method according to claim 43, wherein saidstep of interleaving the modulation-encoded data interleaves themodulation-encoded data in terms of a modulation encoding block as aunit.
 53. The data recording and reproducing method according to claim43, wherein said step of applying modulation encodes input data inaccordance with the trellis conforming to said constraint condition; andsaid step of modulation decoding performs decoding based on a trellisconforming to said constraint condition.
 54. The data recording andreproducing method according to claim 53, wherein said step ofinterleaving the modulation-encoded data interleaves themodulation-encoded data in terms of a modulation encoding block of saidtrellis as a unit.
 55. The data recording and reproducing methodaccording to claim 44, wherein said modulation decoding step performssoft output decoding based on the BCJR algorithm or on the SOVAalgorithm.
 56. The data recording and reproducing method according toclaim 43, wherein data is recorded on said recording medium by amagnetic, optical or magneto-optical system.